System and method for electronic inventory

Abstract

A system and method for conducting an inventory of tags, wherein each tag is assigned a Tag ID and a manufacturer number. Each tag can be attached to an item to take inventory of those items. A tag reader transmits a wake-up signal followed by at least one clock signal. Each tag increments a first tag count in response to the clock signals, and transmits the Tag ID assigned to the tag when the first tag count corresponds to the Tag ID assigned to the tag. The tag reader records the transmitted Tag IDs. When more than one tag transmits simultaneously, the tag stores the Tag ID in order to resolve the contention when the first read cycle is complete. In the second read cycle, the tag reader transmits the contended Tag ID followed by at least one clock signal. Each tag that contended for the transmitted Tag ID increments a second tag count in response to the clock signals, and transmits the manufacturer number assigned to the tag when the second tag count corresponds to the manufacturer number assigned to the tag. The tag reader records the transmitted Tag IDs, completing the inventory of the tags.

1 - 91 . (canceled)  
   
   
       92 . An inventory system, comprising a plurality of radio frequency identification (RFID) tags and a tag reader, wherein at least one RFID tag responds to said tag reader during one of a plurality of time slots, and said tag reader performs multiple reads of said RFID tags to avoid contention when two or more RFID tags respond during the same time slot, wherein said RFID tag is identified by a plurality of bits, wherein said RFID tag responds to said tag reader with a first plurality of said plurality of bits during a first read and a second plurality of said plurality of bits during a second read.  
   
   
       93 . The system of  claim 92 , wherein said tag responds to said tag reader within a time slot defined by at least a plurality of said plurality of bits.  
   
   
       94 . The system of  claim 92 , wherein one of said RFID tags includes a sensor.  
   
   
       95 . The system of  claim 92 , wherein said tag reader is configured to transmit a first value corresponding to said first plurality of said plurality of bits of a tag to be located and a second value corresponding to said second plurality of said plurality of bits of a tag to be located.  
   
   
       96 . The system of  claim 95 , wherein said tag transmits, in response to receiving said first value, said first plurality of said plurality of bits assigned to said tag when said first plurality of said plurality of bits corresponds to said first value, wherein said tag further transmits, in response to receiving said second value, said second plurality of said plurality of bits assigned to said tag when said second plurality of said plurality of bits corresponds to said second value.  
   
   
       97 . The system of  claim 96 , wherein said tag is further identified by a third plurality of said plurality of bits, wherein said tag reader is further configured to transmit a third value corresponding to said third plurality of said plurality of bits of a tag to be located, wherein said tag transmits, in response to receiving said third value, said third plurality of said plurality of bits corresponding to said third value.  
   
   
       98 . The system of  claim 96 , wherein said tag includes a sensor.  
   
   
       99 . The system of  claim 92 , wherein at least one of said RFID tags is attached to a piece of merchandise.  
   
   
       100 . The system of  claim 99 , wherein at least one of said RFID tags is manufactured on a flexible substrate.  
   
   
       101 . The system of  claim 92 , wherein said tag reader is further configured to transmit a wake-up signal.  
   
   
       102 . The system of  claim 92 , wherein at least one of said RFID tags is manufactured on a flexible substrate.  
   
   
       103 . The system of  claim 92 , wherein said RFID tags are configured to receive and transmit signals.  
   
   
       104 . The system of  claim 92 , wherein said RFID tags are configured to receive a signal from said tag reader, evaluate said signal relative to said first plurality of said plurality of bits or second plurality of said plurality of bits, and reply to said signal when appropriate.  
   
   
       105 . The system of  claim 104 , wherein at least one of said plurality of RFID tags has a sensor; and means for transmitting the contents of said sensor.  
   
   
       106 . The system of  claim 104 , wherein said tag reader emits a series of clock signals, each clock signal defines a time slot, and said signal is a clock signal.  
   
   
       107 . The system of  claim 106 , wherein each RFID tag begins a count based on said clock signal and when said count is equivalent to said first plurality of said plurality of bits, transmits its reply to said tag reader.  
   
   
       108 . The system of  claim 106 , wherein said tag reader polls all tags whose reply conflicted with another tag.  
   
   
       109 . The system of  claim 92 , wherein said tag reader can initiate an immediate read of said RFID tags, a specific RFID tag read, or a timed broadcast read of said RFID tags.  
   
   
       110 . The system of  claim 92 , wherein said tag reader emits a series of clock signals, each clock signal defines a time slot, wherein each said RFID tag responds during a time slot defined by data stored on each said RFID tag.  
   
   
       111 . The system of  claim 110 , wherein said data is at least some of said plurality of bits.  
   
   
       112 . The system of  claim 92 , wherein said tag reader includes a PCMCIA card that is configured for a specific application.  
   
   
       113 . A radio frequency identification (RFID) tag that is interrogated by a tag reader, comprising: 
 means for receiving a first signal from the tag reader, the tag reader performs multiple reads of the RFID tag to avoid time slot contention, wherein the tag is identified by a plurality of bits, and wherein the tag responds to the tag reader during one of a plurality of time slots; and    means for transmitting a second signal to the tag reader in response to receiving said first signal from the tag reader, wherein said second signal includes a first plurality of said plurality of bits during a first read and a second plurality of said plurality of bits during a second read from the tag reader.    
   
   
       114 . The RFID tag of  claim 113 , wherein the tag responds to the tag reader within a time slot defined by said first or second plurality of said plurality of bits.  
   
   
       115 . The RFID tag of  claim 113 , wherein the tag further includes a sensor.  
   
   
       116 . The RFID tag of  claim 113 , wherein the tag is attached to a piece of merchandise.  
   
   
       117 . The RFID tag of  claim 116 , wherein the tag is manufactured on a flexible substrate.  
   
   
       118 . The RFID tag of  claim 113 , wherein the tag is configured to evaluate said signal relative to said first plurality of said plurality of bits or second plurality of said plurality of bits, and reply to said signal when appropriate.  
   
   
       119 . The RFID tag of  claim 118 , wherein the tag further comprising: 
 means for incrementing a first tag count in response to receiving a first clock signal;    means for transmitting said first plurality of said plurality of bits assigned to the tag when said first plurality of said plurality of bits of the tag corresponds to said first tag count;    means for incrementing a second tag count in response to receiving said second clock signal; and    means for transmitting said second plurality of said plurality of bits assigned to the tag when said second plurality of said plurality of bits of the tag corresponds to said second tag count.    
   
   
       120 . The RFID tag of  claim 113 , wherein said first signal comprises a clock signal.  
   
   
       121 . A method for conducting an electronic inventory of radio frequency identification tags, the method comprising the steps of: 
 (A) transmitting a first signal to a plurality of radio frequency identification (RFID) tags, wherein each said tag is identified by a plurality of bits, wherein said RFID tags are configured to receive and transmit signals;    (B) receiving a reply from said plurality of RFID tags during one of a plurality of time slots, said tags responding to said first signal based on the value of a first plurality of said plurality of bits; and    (C) resolving contention between multiple RFID tags if at least two of said RFID tags respond during the same time slot to said first signal, including transmitting a second signal to said plurality of RFID tags.    
   
   
       122 . The method of  claim 121 , wherein at least one of said RFID tags includes a sensor, the method further including receiving sensor data from said at least one of said RFID tags.  
   
   
       123 . The method of  claim 121 , further comprising receiving a reply to said second signal from at least one RFID tag based on the value of a second plurality of said plurality of bits.  
   
   
       124 . The method of  claim 121 , further comprising transmitting a first value corresponding to said first plurality of said plurality of bits of a tag to be located and a second value corresponding to said second plurality of said plurality of bits of a tag to be located.  
   
   
       125 . The method of  claim 124 , further comprising transmitting, in response to receiving said first value, said first plurality of said plurality of bits assigned to said tag when said first plurality of said plurality of bits corresponds to said first value, wherein said tag further transmits, in response to receiving said second value, said second plurality of said plurality of bits assigned to said tag when the second plurality of said plurality of bits corresponds to said second value.  
   
   
       126 . The method of  claim 125 , wherein said tag is further identified by a third plurality of said plurality of bits, wherein the method further comprising transmitting a third value corresponding to said third plurality of said plurality of bits of a tag to be located, wherein said tag transmits, in response to receiving said third value, said third plurality of said plurality of bits corresponding to said third value.  
   
   
       127 . The method of  claim 126 , further comprising attaching at least one of said RFID tags to a piece of merchandise.  
   
   
       128 . The method of  claim 127 , further comprising manufacturing at least one of said RFID on a flexible substrate.  
   
   
       129 . The method of  claim 121 , further comprising transmitting a wake-up signal.  
   
   
       130 . The method of  claim 121 , wherein said first signal and second signal are a clock signals, wherein each clock signal defines a time slot.  
   
   
       131 . The method of  claim 130 , wherein each RFID, tag begins a count based on said clock signal and when said count is equivalent to said first plurality of said plurality of bits, transmits its reply to said tag reader.  
   
   
       132 . The method of  claim 121 , further comprising initiating an immediate read of said RFID tags, a specific RFID tag read, or a timed broadcast read of said RFID tags.